<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script>
        /**
         * if语句
         * if(条件表达式){
         *      语句1
         * }else{
         *      语句2
         * }
         * 
         * 
        */

        var a = 10;
        if (a >= 5) {
            alert("a大于等于5");
        } else {
            alert("a小于5");
        }
    </script>
</head>
<body>
    
</body>
</html>